Ma bonté! We're all Spanish...

But the truth could be very different, with modern Britons having more in common with the laid-back Spaniards.

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A new book by Oxford University researcher Dr Stephen Oppenheimer claims that up to three-quarters of our genes were inherited from the Basques of northern Spain.

He believes the Basques arrived around 15,000 years ago - significantly earlier than either the Celts or the Anglo-Saxons - and at time when the British Isles were still joined to the rest of Europe.

Britain was unpopulated then, wiped clean of people by glaciers that had smothered northern Europe for thousands of years and forced the former inhabitants into southern refuges in Spain and Italy.

When the climate warmed, and the glaciers retreated, the people, who lived by hunting and gathering, moved back north.

It is thought agriculture was introduced by the Celts on their arrival around 6,000 years ago, after rising sea levels divided Britain and Ireland from the Continent and one another.

They were followed by the Romans, Anglo-Saxons, Vikings and Normans.

None, however, had as great an influence on our blood line as the Basques, Dr Oppenheimer argues in his book "The Origins of the British: A Genetic Detective Story".

The retired paediatrician, who dismisses the influence of the Celts and Anglo-Saxons on our heritage as a "big myth", said: "The majority of the gene pool of the British Isles is very ancient and dates to the era after the last great Ice Age.

"It has nothing to do with the Celts or the Anglo-Saxons or any of these more recent ethnic labels.

"The Ice Age made Britain a polar desert and there was no one living here until the first settlers came to the British Isles from the Basque country of northern Spain between 15,000 and 7,000 years ago.

"Something like three-quarters of the ancestors of our modern gene poll arrived then."

His research - which involved pinpointing the geographical distribution of mutations in key genes - also suggests that the various peoples of the British Isles have more in common than they might like to think.

He said: "The ancestors of some 88 per cent of the Irish, 81 per cent of the Welsh, 79 per cent of the Cornish, 70 per cent of the Scots and 68 per cent of the English arrived here during that period.

"None of the later immigrations contributed anything more than five per cent to the gene pool.

"So genetically speaking, Scots have more in common with the English than they have differences."

But other geneticists say our heritage remains unclear.

Dr Chris Tyler-Smith, of the Wellcome Trust Sanger Institute, near Cambridge, said: "North-west Europeans are all fairly similar to one another genetically, so there is a lot of similarity between the Basques and the British.

"But I think it is difficult to jump from that to saying one set of people originated from the other."

The Origins of British History: A Genetic Detective Story is published by Constable & Robinson and costs £20.